I wonder why many members use old machines to install linux, and why install the last releases of the more resources consumers distros like opensuse, fedora, ubuntu. And do not use lightweight options.
I run CentOS 5.8 on my Low-end Virtual private Sever, it has 256 MB of RAM(Main Memory, no Burst), 10 GB of Disk space and a good amount of Data transfer on a 100 mbit downlink network.
The reason is quite simple, If you can't run heavy-performance OS's on your old machines, you have to find an alternative. Linux has many alternatives.